Oil upgrader catalyst, such as a standard hydrotreating/HDS catalyst manufactured by Akzo Chemie Nederaland by Amsterdam, and identified as Ketjenfine1™ 742-1, 3AQ, has been used in prior art oilfield in situ hydrocarbon upgrading processes of the type described in U.S. Pat. No. 6,412,557. 1 Trademark of Akzo Chemie Nederaland by Amsterdam for hydrotreating catalyst
Specifically, U.S. Pat. No. 6,412,557 describes a process for upgrading hydrocarbons within a petroleum reservoir by placing such a known hydrotreating catalyst around an exterior periphery of a centrally located perforated pipe situated in the horizontal leg of a horizontal well bore for upgrading and producing oil from a heavy oil (bitumen) formation.
Specifically, as may be understood from the in situ upgrading process of U.S. Pat. No. 6,412,557 and the methodology of the prior art in relation to in situ oil upgrading, a hole is drilled from the surface down to the target reservoir oil zone of the petroleum formation. The hole is curved so that it becomes horizontal when it arrives at the target reservoir oil zone. The horizontal section is typically created near the lowermost base portion of the target reservoir zone, and is extended laterally along the lowermost base portion to create a horizontal well, typically extending for hundreds of meters to the intended toe of the horizontal well. The vertical section of such well is cased. If the reservoir rock is consolidated, the horizontal section may be left open and un-cased, but sometimes a perforated liner is emplaced in the horizontal section to mitigate against the production of sand fines. If the rock is un-consolidated it is imperative to emplace a perforated liner to prevent complete collapse of the hole. Once drilling of the hole is completed a metal pipe is pushed into the hole, typically all the way to the intended toe of the horizontal well. In the horizontal section, this pipe is referred-to as the ‘liner’. The liner will have openings that are sized to allow reservoir fluids to enter the interior of the liner for flowing to the surface, but exclude the entry of sand that could plug the liner or cause operational difficulty with oil treating facilities at the surface. The openings in the liner can be narrow slits, in which case the pipe is called a ‘slotted liner’, or they may be narrow apertures between rows of wire that is wrapped around a pipe having relatively large holes, which are called ‘wire-wrapped screens’. Both slotted liners and wire-wrapped screens are commonplace in the design of horizontal wells. The separation of the liner from the undisturbed reservoir is small, typically in the range of 1-2 inches based on a centralized liner. While the bore hole may be drilled larger by reaming operations to leave more space between the liner and the reservoir, this is an additional expense.
As taught in the prior art and for example U.S. Pat. No. 6,412,557, the 1-2 inch annular interstitial space which exists between an un-reamed hole (typically approximately 12.25 inches in diameter) and the outside diameter of the centralized liner (typically of in the range of about 9.6 inches) is filled with catalyst of the type described above or a similar catalyst, by pumping such catalyst downhole into such interstitial space. The catalyst permits upgrading of the oil immediately prior to entering the perforated well liner so as to increase flowability of the produced oil within the horizontal well to more easily produce such oil to surface.
Disadvantageously, however, with this prior art method, since the resulting vertical path of draining fluids (oil) into the perforated liner is very short, the residence time of the oil in the interstitial space which contains such catalyst is very short, and the Gas and Liquid Hourly Space Velocity (“LHSV”) will be very high. By way of example, for a well of the above dimensions producing 100 m3/day of produced oil having a well 1-inch annular catalyst zone, the LHSV is approximately 2670 hr−1 and the residence time is only approximately 11 seconds. While this short residence time may provide some upgrading, it would be much more desirable to have a catalyst placement design that provides much longer residence times for the oil being exposed to such upgrading catalyst.
Accordingly, a real need exists for a liner design and an improved oilfield in situ hydrocarbon upgrading process which allows increased time of exposure of the produced oil to upgrader catalyst, to thereby improve flowability and increase effective recovery from underground petroleum formations, particularly from bitumen and tar sands formations.